Safety multi-optical axis photoelectric sensor

ABSTRACT

The present invention can be used in a multi-optical axis photoelectric sensor indicating an operating status thereof to a non-safety control device. The present invention allows the multi-optical axis photoelectric sensor so as to become a easier operation. The multi-optical axis photoelectric sensor has a control unit to providing a safety control signal representing a result of a distinguish portion in a normal operating status, a safety control signal representing operation non-allowable in an abnormal status and a safety control signal representing operation allowable in a special operating status. The multi-optical axis photoelectric sensor also has an operating status indication portion for determining an operating status of the multi-optical axis photoelectric sensor from the normal operating status, the abnormal status and the special operating status, and providing the operating status to an external device via the same output line regardless of the result of the determination.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2007-015148, filed on Jan. 25, 2007, the entire contents of whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multi-optical axis photoelectricsensor forming a light curtain for detecting a human body and the likepenetrating into a predetermined area. In more detail, the presentinvention relates to an output of the multi-optical axis photoelectricsensor provided for a non-safety control device.

2. Description of the Related Art

In general cases, a multi-optical axis photoelectric sensor fordetecting a human body and the like, is utilized where a person can comein contact with a hazardous source, thereby providing safety to theperson in view of a machine which is assessed as the hazardous sourcesuch as a press machine. The multi-optical axis photoelectric sensorincludes: an emitting unit having a plurality of emitting elementsarranged in a line; and a receiving unit having a plurality of receivingelements which receive light beams from the plurality of emittingelements and arranged in a line. A light curtain is formed by aplurality of light beams between the emitting unit and the receivingunit, to separate the hazardous source from the other area. In casewhere an object penetrates into the light curtain, the multi-opticalaxis photoelectric sensor detects that the light beam is intercepted(blocked). In this case, the multi-optical axis photoelectric sensoroutputs a cutout signal for cutting out a power supply to a motor andthe like which drives the hazardous source.

The multi-optical axis photoelectric sensor including various kinds ofspecial functions has been developed. This is shown, for example, inJapanese published patent No. 2003-218679. The special functions are,for example, a muting function, an override function etc. as describedbelow.

The “Muting function” is a function to temporarily disable the detectionfunction of the multi-optical axis photoelectric sensor in response to asignal received (“muting signal”, hereinafter) from an external mutingsensor. When the muting function is activated, the multi-optical axisphotoelectric sensor temporarily provides a safety control signalrepresenting an operation allowable even if the light beam is blocked.In detail, the safety control signal representing the operationallowable is ON state signal.

A photoelectric sensor and a limit switch are suitable for the mutingsensor. A status of the multi-optical axis photoelectric sensor isshifted to a status in which the muting function is activated (“mutingstatus”, hereinafter) when a condition regarding the multi-optical axisphotoelectric sensor meets the requirement that all of the light beamsof the multi-optical axis photoelectric sensor pass through in a normalmode (normal operating status), namely the safety control signal is ONstate, and the muting signal is received. On the other hand, when thecondition regarding the multi-optical axis photoelectric sensor does notmeet the requirement, for example, a) one of any light beams isintercepted in the normal mode, namely the safety control signal is OFFstate or b) an abnormal status is detected by a self check function ofthe multi-optical axis photoelectric sensor, a shifting into the mutingstatus is not performed even if the muting signal is received.

The multi-optical axis photoelectric sensor has the self check functionfor watching fault itself, an abnormal condition from external noisesetc. all the time. In case where at least one fault and some abnormalcondition is detected by the self check function, a safety controlsignal representing an operation non-allowable is provided even if allof the light beams for detecting the object are passed through. In somecases, a product line is suspended when a product machine is cut offbased on the safety control signal representing an operationnon-allowable signal. In such a case, productivity may decrease. On theother hand, the multi-optical axis photoelectric sensor outputs thesafety control signal representing an operation non-allowable signal inaccordance with an improper user's operation for setting an additionalfunction such as the muting function since the multi-optical axisphotoelectric sensor is developed under the fail safe concept.

Referring to FIG. 5, an example of system installing the muting functionwill be described.

In FIG. 5A, a robot 101 and a processing machine M are disposed in anarea surrounded by protective fences. The protective fences have anopening for a path passed by an operator O who carries an object W intothe area. The emitting unit 2 and the receiving unit 3 are placed infront of the opening. Consequently, the light curtain, namely adetection area A, is formed corresponding to the opening in order todetect the operator O existing at the opening of the protective fences.

As shown in FIG. 5B, a rotating motion of an arm 102 is locked by a rod105 of a cylinder 104 when the emitting unit 2 and the receiving unit 3of the multi-optical axis photoelectric sensor does not detect anoperator O penetrating into the detection area A. Then, the lock statusis detected by, for example, an optical sensor 110. The optical sensor110 is connected to a muting input terminal of the multi-optical axisphotoelectric sensor. Thus, the status of the multi-optical axisphotoelectric sensor is shifted to muting status based on the mutingsignal from the optical sensor 110. Consequently, the operator O ispermitted to enter the detection area A to carry the object W on a rest100.

The robot 101 rotates the arm 102, and provides the object W disposed onthe rest 100 in an operation area, and the robot 101 carries it to aprocessing machine M. The robot 101 is able to rotate only when the rod105 of the cylinder 104 equipped at a rotating unit 103 as shown in FIG.5D is located downwardly. The robot 101 is not allowed to rotate in thecase of FIG. 5B. Therefore, safety for the operator O in the detectionarea A is secured although the operator O is located in the detectionarea A.

In case of restarting of the robot 101 to operate, as shown in FIG. 5C,the operator O goes out from the detection area A and pushes a startbutton 107 of an operational panel 106. Consequently, the rod 105 movesdownwardly as shown in FIG. 5D. Therefore, the muting status is canceledsince a requirement for maintaining the muting status is not met basedon passing through of the optical sensor 110. In this case, the arm 102shown in FIG. 5C rotates and puts the object W on the rest 100.

However, for example, in case where the operator O does not exit fromthe detection area A completely and reaches for the start button 107, acareless stop occurs in that part of the industrial system since themuting status is canceled and the light beam is stilt intercepted by theoperator O.

When the multi-optical axis photoelectric sensor detects the object onthe light curtain, the safety control signal becomes OFF state. Thisstatus is an interlock status. There are two ways to return from theinterlock status to the normal operating status.

One way is to automatically reset; that is, a requirement for returningto the normal operating status is that all light beams passed through.

The other way is to manually reset; that is, a requirement for returningto the normal operating status is not only that all light beam arepassed through, but also that an interlock reset signal is provided. Inthe case of an interlock by manually reset, an operator pushes aninterlock reset button to reset the interlock of the multi-optical axisphotoelectric sensor. However, the operator can not know whether themulti-optical axis photoelectric sensor has been prepared for receivingthe interlock reset signal or not. The operator does not know whetherthe interlock was reset or not, either.

To control the multi-optical axis photoelectric sensor via a non-safetycontroller, such as a PLC (Programmable Logic Controller) may solvethese problems, but safety regulations may not permit one to control thesafety component via a non-safety controller. Thus, these problems stillremain.

SUMMARY OF THE INVENTION

The present invention solves such drawbacks of the conventionaltechnique. An object of the present invention is to provide amulti-optical axis photoelectric sensor capable of reducing waiting timefor completely changing the status of the multi-optical axisphotoelectric sensor and to prevent mistaken operation for an operatorand to secure safety.

According to the present invention, the above technical problem can besolved by providing a multi-optical axis photoelectric sensor thatincludes a plurality of light axes to provide a safety control signalcorresponding to light pass/block status of the plurality of light axes,having a distinguish portion for distinguishing whether all of theplurality of light axes are passed through or at least one of theplurality of light axes is blocked; a detector to detect an abnormalcondition of the multi-optical axis photoelectric sensor; a control unitto control the safety control signal based on the result distinguishedby the distinguish portion and the result detected by the detector,wherein the control unit sets the safety control signal representing theresult distinguished by the distinguish portion on a normal operatingstatus, the control unit sets the safety control signal representingthat at least one of the plurality of light axes is blocked regardlessof the result distinguished by the distinguish portion on an abnormalstatus detected by the detector, and the control unit sets the safetycontrol signal representing all of the plurality of light axes arepassed through regardless of the result distinguished by the distinguishportion on a special operating status; and an operating statusindicating portion for determining an operating status of themulti-optical axis photoelectric sensor from the normal operatingstatus, the abnormal status and the special operating status and forindicating the determined operating status of the multi-optical axisphotoelectric sensor to an external device via the same output lineregardless of the determined operating status.

According to the present invention, the operating status indicatingportion may indicate a shifting of the operating status.

According to the present invention, the same output line may include aplurality of individual lines, and the operating status indicatingportion may provide a first signal having pulses of the numbercorresponding to the operating status via one of the plurality ofindividual lines and a second signal representing whether the firstsignal is enabled or not via another of the plurality of individuallines.

According to the present invention, the same output line may include aplurality of individual lines, and the operating status indicatingportion may provide binary code made by a combination of a plurality ofON/OFF state signals via each of the plurality of individual lines.

According to the present invention, the control unit may be controlledso as to shift the multi-optical axis photoelectric sensor to a mutingstatus as the special operating status based on receiving a mutinginput.

According to the present invention, the control unit may be controlledso as to shift the multi-optical axis photoelectric sensor to a mutingstatus as the special operating status based on receiving a muting inputin only case where the distinguish portion distinguishes that all of theplurality of light axes are passed through.

According to the present invention, the control unit may be controlledso as to shift the multi-optical axis photoelectric sensor to anoverride status as the special operating status based on receiving amuting input and an override input.

According to the present invention, the control unit may be controlledso as to shift the multi-optical axis photoelectric sensor to anoverride status as the special operating status based on receiving amuting input and an override input in the case where the distinguishportion distinguishes that at least one of the plurality of light axesis blocked.

According to the present invention, the operating status indicatingportion may not indicate the operating status of the multi-optical axisphotoelectric sensor or may indicate an unidentified operating statusuntil verification of shifting the operating status at the power “on”period.

According to the present invention, the operating status indicatingportion may not indicate the operating status of the multi-optical axisphotoelectric sensor or may indicate unidentified operating status untilverification of shifting the operating status at the shifting period.

With a multi-optical axis photoelectric sensor according to the presentinvention, an operator and the like are safely secured since a safetycontrol output is received by a safety control device. Moreover,information about an operating status of the multi-optical axisphotoelectric sensor is provided from an operating status indicatingmeans, and is received by a non-safety control device. The non-safetycontrol device has no obligation related to the safety regulations.Thus, the non-safety control device is capable of controlling in variousways. For example, the multi-optical axis photoelectric sensor iscapable of providing information indicating whether the multi-opticalaxis photoelectric sensor is preparing for resetting an interlock ornot. Further, the number of output lines can be restrained to increasethe number of output lines since the information regarding the operatingstatus indicated to an external device can be sent via the same line aseach operating status.

The “normal operating status” is a status defined by the state of thesafety control signal that turns ON/OFF (representing operationallowable/operation non-allowable or stop signal) in accordance with thecondition whether the light beam of the multi-optical axis photoelectricsensor is passed through or intercepted. In more detail, the state ofthe safety control signal turns ON/OFF in response to a status whetherall of the light beams of the multi-optical axis photoelectric sensorare passed through or at least one of any light beams of themulti-optical axis photoelectric sensor is intercepted in the normaloperating status.

The “abnormal status such as emitting error, receiving error,communicating error, connecting configuration error, output error andmuting lamp fault” is a status defined by a state of the safety controlsignal maintained in OFF state (representing operating non-allowable orstop) regardless of the condition whether the light beam of themulti-optical axis photoelectric sensor is passed through orintercepted. When an error or fault is detected, the multi-optical axisphotoelectric sensor is shifted to the “abnormal status”. There arevarious causes for error and fault. One of preferred embodiments is toindicate each status of the multi-optical axis photoelectric sensorcorresponding to each cause. Another preferred embodiment is to indicatethe “abnormal status” regardless of the causes. To shift the “abnormalstatus” to the “normal operating status” is performed in response to thesame manner as in the “interlock”. That is, in the case where all of thelight beams are passed through, the multi-optical axis photoelectricsensor is allowed to shift to the “normal operating status” in responseto receiving the reset input. On the other hand, in the case where oneof any light beams is intercepted, the multi-optical axis photoelectricsensor is allowed to shift to the “normal operating status” regardlessof receiving the reset input.

As one of the preferred embodiments, a multi-optical axis photoelectricsensor has a muting lamp port for directly connecting to a muting lamp.The muting lamp port does not only provide current for the connectedmuting lamp, but is also connected to a detecting circuit for inspectingthe current passing into the lamp. When the current passed into the lampis not normal, the status is determined as the abnormal status since themuting function is temporarily disabled from at least a part of thefunction of the multi-optical axis photoelectric sensor, and themulti-optical axis photoelectric sensor is capable of connecting to anexternal muting lamp to indicate the status easily. Accordingly, toindicate that the muting lamp is not in a proper status is important.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing a multi-optical axisphotoelectric sensor according to a first embodiment;

FIG. 2A is a schematic block diagram showing a controller, a non-safetycontrol device and safety control device;

FIG. 2B is a diagram showing a pulse signal from a controller to anon-safety device;

FIG. 3 is a timing chart showing an example of operation for a systemwith a multi-optical axis photoelectric sensor;

FIG. 4 is a timing chart showing another example of operation for asystem with a multi-optical axis photoelectric sensor;

FIG. 5A is a schematic plan view showing another example of operationfor a system with a multi-optical axis photoelectric sensor;

FIG. 5B is a schematic side view showing a mechanical lock mechanism;

FIG. 5C is a schematic plan view showing another example of operationfor a system with a multi-optical axis photoelectric sensor;

FIG. 5D is a schematic side view showing a mechanical lock mechanism;

FIG. 6 is an example of a flowchart regarding a non-safety controldevice;

FIG. 7 is an example of a flowchart showing the resetting of aninterlock regarding a safety control device; and

FIG. 8 is a schematic block diagram showing a multi-optical axisphotoelectric sensor according to the first embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present invention, when an operating status indicating means isset to providing a signal at only a timing of shifting of the operatingstatus, a few output wires are capable of providing each signalcorresponding to various kinds of statuses since the signal is notrequired to output all the time.

In the present invention, the same output line includes a plurality ofoutput individual wires. In this case, the operating status indicatingmeans provides a signal representing an operating status of themulti-optical axis photoelectric sensor with the number of pulses ofpulsed signal via one group of the plurality of wires, and indicates anenabled timing of the pulsed signal via another of the plurality ofwires. Consequently, various kinds of status are indicated via twoindividual lines.

In the present invention, the same output line includes a plurality ofoutput wires. The operating status indicating means may indicate theoperating status with a binary code from combination of ON/OFF state ofa plurality of wires.

In the present invention, a special operating status of themulti-optical axis photoelectric sensor may be a muting status in whicha safety control signal representing operation allowable is temporarilyprovided in response to an external muting input regardless of theresult of the determination by a distinguish means.

Further, as the present invention, a status of the multi-photoelectricsensor may be shifted from the normal operating status to the mutingfunction activating status in the case where the distinguish meansdetermines that all of the light beam 3 are passed through.

In the present invention, the special operating status may be anoverride status in which a safety control signal representing operationallowable is temporarily provided in response to an external mutinginput and an override input in case where the distinguish meansdetermines that one of any light beams is blocked.

Further, as the present invention, a status of the multi-optical axisphotoelectric sensor may be shifted from the normal operating status tothe overriding status in the case where the distinguish means determinesthat one of any light beams is blocked and an external muting input isreceived.

As the present invention, after power on, the operating statusindicating means may not indicate any signals representing operatingstatus until confirming the operating status. Alternatively, after poweron, the operating status indicating means may be indicated as anundefined status until confirming the operating status. As a result, inan initial period after power on, the operating status indicating meanscan be prevented from providing incorrect information although theoperating status is undefined.

In the present invention, the operating status indicating means may notindicate any operating statuses at the shifting of the operating statusuntil confirming the shifted operating status. Alternatively, afterpower on, the operating status indicating means may be indicated as anundefined status until confirming of the operating status. As a result,in a shifting period, the operating status indicating means can beprevented from providing incorrect information although the operatingstatus is undefined.

First Embodiment Multi-Optical Axis Photoelectric Sensor 1

In FIG. 1, a multi-optical axis photoelectric sensor 1 of the presentinvention includes a pair of an emitting unit 2 and a receiving unit 3,and controller 5 is installed in the receiving unit 3. The controller 5is connected to the emitting unit 2 via a communication line or a signalline L1.

The emitting unit 2 and the receiving unit 3 are arranged in a plane andfaces to each other in a plane. A plurality of light beams such asinfrared light beams are emitted from each of a plurality of emittingelements 7 of the emitting unit 2 to each of a plurality of receivingelements 8, corresponding to each of the plurality of emitting elements7, of the receiving unit 3. Consequently, a safety light curtain isformed between the emitting unit 2 and the receiving unit 3. Referencenumber 10 as shown in FIG. 10 represents a light axis.

The emitting element 7 constitutes, for example, a light emitting diode(LED) emitting an infrared light. On the other hand, the receivingelement 8 constitutes, for example, a photo diode. A condenser lens, notshown, is disposed in front of each of the plurality of the emittingelements 7 and the plurality of the receiving elements 8.

The emitting unit 2 includes the emitting element 7 of N unit, anemitting circuit 12 of N unit for driving the emitting element 7 of Nunit respectively, an element switching circuit 13 for scanning theemitting element 7 of N unit with time-sharing, and an emitting controlcircuit 14 for controlling the emitting unit 2 as a whole. The emittingcontrol circuit 14 receives a clock signal generated by a clockgenerating circuit 15. Then, the emitting control circuit 14 determinesan emitting timing in response to the clock signal so that the emittingelement of N unit emits corresponding to the emitting timing in turn.

The emitting unit 2 has a communication control circuit 17 forcontrolling communication with the controller 5 and the receiving unit 3such as an interchange of a timing signal. The emitting control circuit14 activates the emitting circuit 12 of N unit in turn in response toreceiving an instruction from the controller 5. Then, the emittingelements 7 are controlled to emit in turn from first light axis 10 toN-th of the light axis 10. As a result, the emitting unit 2 emits thelight beam in turn from the first light axis 10 to the light axis 10 ofN-th to the receiving unit 3.

The receiving unit 3 includes the receiving unit 8 of N unit, areceiving circuit 18 of N unit for driving the receiving element 8 of Nunit respectively, an element switching circuit 19 for scanning thereceiving element 8 of N unit with time-sharing, and an receivingcontrol unit 20 for controlling the receiving unit 3 as a whole. Thereceiving control unit 20 receives a clock signal generated by a clockgenerating circuit 21. Then, the receiving control unit 20 determines areceiving timing in response to the clock signal so that the receivingelement of N unit activates to receive corresponding to the receivingtiming in turn.

The receiving unit 3 has a communication control circuit 23 forcontrolling communication with the controller 5 and the emitting unit 2such as an interchange of a timing signal. The receiving control unit 20activates the receiving circuit 18 of N unit in turn in response toreceiving an instruction from the controller 5. Then, the receivingelements 8 are controlled to receive in turn from first light axis 10 toN-th of the light axis 10. As the result, the receiving unit 3 receivesthe light beam in turn from the first light axis 10 to the light axis 10of N-th to the receiving unit 3.

A receiving signal (representing each light axis is passed through orintercepted) from the receiving element 8 is provided to the receivingcontrol unit 20 via the respective circuit of the receiving unit 3. Indetail, a distinguish means 33 of the receiving control unit 20distinguishes into binary statuses corresponding to a first status whereall of the light axes 10 are passed through or a second status where atleast one of any light axes 10 is intercepted, based on the output fromthe receiving element 8.

As shown in FIG. 2A, the controller 5 includes an operation indicatingmeans 53, a detection means 34C and a control unit 50. The multi-opticalaxis photoelectric sensor 1 has various kinds of operating statusesdescribed below. The operating status indicating means 53 has a functionof checking a current operating status as described below.

The multi-optical axis photoelectric sensor 1 equips the emittingcontrol circuit 14, the receiving control unit 20, the controller 5 (inFIG. 2A) and detection means 34A-34 c in order to detect (self-check) afault of the multi-optical axis photoelectric sensor 1 itself and anyabnormal status caused by external noise. For example, the detectionmeans 34B as shown in FIG. 1 detects that the receiving circuit 18operates normally, that the element switching circuit 19 switches thereceiving circuit 18 to activate only one receiving circuit 18 at thesame time, and that the communication control circuit 23 and the outputcircuit operates normally. In more detail, for example, in the case ofchecking the output circuit, when the receiving unit 3 receives thelight from the emitting unit 2, an ON state signal as an emitting enablesignal is suspended (output OFF signal) in an extremely short time rangeand periodically. Then, the detection means 34B detects whether theoutput circuit can output the stop status or not. Consequently, a faultof a transistor or the like of the output circuit can be detected allthe time. The detection means 34B checks fault of the multi-optical axisphotoelectric sensor 1 all the time since such self-checking isrepeatedly performed.

The self-checking method for detecting an abnormal status of amulti-optical axis photoelectric sensor 1 is well-known. As anothermethod, a method to detect an abnormal status based on a result of themeasurement of whether a predetermined current is passed or not at anemitting timing so as to determine whether any of two or more emittingelements of the emitting unit emit simultaneously, and a method forchecking an external light noise based on a receiving status of areceiving element at a non-emitting timing, and the combination can beused.

The multi-optical axis photoelectric sensor 1 shown in FIG. 2A has aconnector 6 including a plurality of terminals 61, 62 for connecting toa non-safety control device 4 and a safety control device 9respectively. The non-safety control device 4 and the safety controldevice 9 are connected to the controller 5 respectively.

The safety control device 9 is generally designed such that a redundantcircuit and self-checking function are equipped so that safety issecured even though a fault and an abnormality occurred. A safetycontrol output such as an operation allowable and an operationnon-allowable is output in accordance with an operating status asdescribed following from a control unit 50 of the controller 5 to thesafety control device 9 via the output terminal 62 (OSSD). On the otherhand, a reset input is inputted from the process machine as the safetycontrol device to the controller 5. The non-safety control device 4 iscorresponding to, for example, a PLC, and various kinds of controldevices are suitable to the non-safety control device 4. A muting inputand an override input are inputted from the non-safety control device 4.An interlock mode select IL is an input line for choosing activation ofa restart interlock function.

An operating status indicating means 53 is connected to an output linedescribed below. A symbol “IR” represents an output line for outputtinga signal at waiting for release restart interlock. A symbol “Warn”represents an output line for warning when the light amount is reducedcorresponding to improper alignment of the light axis and/or dirt of thelens surface. A symbol “ST1” and a symbol “ST2” represent an output linefor indicating a status (normal, abnormal, muting, override andinterlock) of the multi-optical axis photoelectric sensor 1 to thenon-safety control device 4. A symbol “C/R” represents an output linefor outputting a status whether all of the light axes is passed throughor at least one of any light axes is intercepted. The safety controloutput concerns not only the status of C/R, but also other statuses. Sothe safety control output does not always match the status of C/R. Asymbol “ML” represents an output line for turning on a muting lamp. Asymbol “AUX” represents a no-safety output corresponding to the safetycontrol output.

Operating Status:

The multi-optical axis photoelectric sensor 1 is capable of being set tovarious kinds of operating status. The operating status includes anormal operating status, an abnormal status, special function status andthe like.

Normal Operating Status;

In the normal operating status, a safety control output corresponding topassed through/intercepted status of the light axes 10 shown in FIG. 1is outputted from the control unit 50.

In a first status where all of the light axes are passed through in anormal operating status, an all-light-passing signal is outputted fromthe distinguish means 33 shown in FIG. 1 to the controller 5. On theother hand, in a second status where at least one of any light axes isintercepted in a normal operating status, an intercepted signal isoutputted from the distinguish means 33 shown in FIG. 1 to thecontroller 5. In the normal operating status, in response to thecontroller 5 receiving the intercepted signal, the control unit 50outputs a safety control output representing operating non-allowable tothe safety control device 9. In the normal operating status, in responseto the controller 5 receiving the all-light-passing signal, the controlunit 50 outputs a safety control output representing operating allowableto the safety control device 9.

In the operating status indicating means 53, for example, a respectiveprogram corresponding to each status exists. When a predeterminedrequirement is met during the running of a program corresponding to onestatus, the operating status indicating means 53 has a means forinitiating a program for another status and a watching function forwatching by determining a shift of the status based on an initiation ofa program for another status.

In the Abnormal Status;

In the present system, the detection means 34A to 34C (shown in FIG. 1and FIG. 2A) described above detects an abnormal status regarding acircuit and the like of the multi-optical axis photoelectric sensor 1.When the circuit and the like of the multi-optical axis photoelectricsensor 1 is detected as an abnormal status, the control unit 50 outputsa safety control output representing operation non-allowable to a safetycontrol device 9 regardless of a signal representing the status ofpassed through or intercepted by the distinguish means 33 (shown in FIG.1).

Special Status:

A function in the special status includes, for example, a mutingfunction and an override function. In the special status, the controlunit 50 outputs a safety control output representing operation allowableto a safety control device 9 regardless of the result distinguished bythe distinguish means 33.

Next, the special functions will be described in more detail.

Muting Function;

A muting function requires a muting input from an external device suchas an optical sensor to be initiated, and is a function for outputting asafety control output representing operation allowable temporarilyregardless of the result of a distinguish by the distinguish means 33(shown in FIG. 1). A shifting from the normal operating status to astatus in the muting function is performed in only case where thedistinguish means 33 determines that all of the light axes 10 are passedthrough.

Override Function;

An override function requires a muting input from an external devicesuch as an optical sensor and an override input to be initiated, and isa function for outputting a safety control output representing operationallowable temporarily regardless of the result of a distinguish by thedistinguish means 33. A shifting from the normal operating status to astatus in the override function is performed in the case where thedistinguish means 33 determines that at least one of any light axes 10is intercepted.

The override function is suitable for an embodiment describedhereinafter.

In the case where an object is transported into a hazardous areautilized by a conveyer, a light curtain is set up at an entrance of thehazardous area. In this case, muting sensors are set up at the forwardand backward locations of the light curtain (the entrance opening) alongthe transporting direction by the conveyer. During the transportedobject is detected by the muting sensor, an operation allowable signalis maintained and outputted from the multi-optical axis photoelectricsensor 1 to the conveyer and, for example, to a process robot in thehazardous area under the muting function even if the transported objectpasses (intercepts) the light curtain. In this case, the conveyer andthe process robot are connected to the safety control output of themulti-optical axis photoelectric sensor 1.

In the case where an unexpected accident such as a time out of themuting function, a momentary break of power supply or various errorsoccur when the muting function is activated and the transported objectintercepts the light curtain, it is difficult to return to the formerstatus. In more detail, in such case, since the multi-optical axisphotoelectric sensor 1 is reset on the status that the light axis isintercepted by the transported object, the muting function can not beactivated even though the muting input is received. In other words, therequirement of shifting to the muting function is that all of the lightaxes are passed through. However, at the time of restart, therequirement is not met because the transported object blocks the lightaxis. Therefore, the shifting from the normal status to the mutingfunction is not performed. Since the safety control output is connectedto the conveyer, the transported object intercepting the light axis cannot be moved via the conveyer from the detection area of themulti-optical axis photoelectric sensor 1. Further, when the objectintercepting the light axis is heavy, the status that the light axis isblocked is maintained since the object can not be moved away.

The override function is suitable for in the above mentioned case. Thus,a requirement for shifting to the override function is that the mutinginput is received, at least one of any light axes is blocked, and anoverride input is received from an external device.

Interlock Function;

When an interlock function is activated, when at least one of any lightaxes is blocked, a shifting to an operating allowable status (one kindof the normal operating status) is not performed until a reset input isreceived even though all of the light axes begin to be passed through.The situation is defined as under a interlock status. A situation whereall of the light axes are passed through under the interlock, is definedas a reset enable status. In the reset enable status, the multi-opticalaxis photoelectric sensor 1 is capable to shift to the operatingallowable status in response to receiving the reset input. On the otherhand, a situation where a part of or all of any light axes are blockedunder the interlock, is defined as a reset disable status. In the resetdisable status, the multi-optical axis photoelectric sensor 1 is notallowed to shift to the operating allowable status even if the resetinput is received.

Shifting of the Operating Status;

The above operating status is set by an setting output from thenon-safety control device 4. The controller 5 determines whether themulti-optical axis photoelectric sensor 1 is capable of shifting to thedesignated operating status or not in response to the setting outputfrom the non-safety control device 4. For example, the operating statusindicating means 53 does not indicate an operating status until theoperating status is specified (confirmed) as the result of thedetermination in the power on stage. In such the case, alternatively,the operating status indicating means 53 may indicate the unstablecondition of the operating status to the non-safety control device 4.

On the other hand, in the case where the operating status is shiftedaccording to the setting output from the non-safety control device 4,the operating status indicating means 53 does not indicate the operatingstatus to the non-safety control device 4 until confirmation of theoperating status is shifted. In this case, alternatively, the operatingstatus indicating means 53 may indicate the unstable condition of theoperating status to the non-safety control device.

In the case where the shifting of the operating status is performed, theoperating status indicating means 53 indicates the new shifted operatingstatus to the non-safety control device 4. The operating statusindicating means 53 distinguishes and indicates in accordance with aprogram of the new operating status.

Safety Control Output:

The control unit 50 outputs the distinguish result from the distinguishmeans 33 shown in FIG. 1 to the safety control device 9 under the normaloperating status. When the distinguish result of the distinguish means33 shown in FIG. 1 is that all of the light axes are passed through, thecontrol unit 50 outputs the safety control output representing theoperation allowable to the safety control device 9. On the other hand,when the distinguish means determines that at least one of any lightaxes is intercepted, the control unit 50 outputs the safety controloutput representing the operation non-allowable to the safety controldevice 9.

In an abnormal condition such that a fault occurs in a circuit of themulti-optical axis photoelectric sensor 1 detected by the detectionmeans 34A to 34 c and an alignment of the light axis becomes improper,the control unit 50 outputs the safety control output representing theoperation non-allowable to the safety control device 9.

In a special operating status of the multi-optical axis photoelectricsensor 1, the control unit 50 outputs the safety control outputrepresenting the operating allowable to the safety control device 9regardless of the distinguish result of the distinguish means 33.

In the above mentioned, the control unit 50 outputs the safety controloutput to the safety control device 9. Simultaneously, the operatingstatus indicating means 53 outputs (indicates) the shifting of theoperating status of the multi-optical axis photoelectric sensor 1 viathe output line including individual lines ST1, ST2 to the non-safetycontrol device 4. The non-safety control device 4 can take the currentoperating status in. Therefore, a device which is free from the safetyregulations, can perform with the various kinds of controls.

Communication Method of Operating Status:

The controller 5 and the non-safety control device 4 are connected toeach other via the output lines SR1, ST2 not shown. The output linesinclude a plurality of output lines. The operating status indicatingmeans 53 provides a pulse signal representing the operating status viathe output line ST2. The number of pulse signals is in accordance withthe operating status. On the other hand, a timing signal for indicatingwhether the pulse signal through the individual output line ST1 is validor not is provided via the individual output line ST1.

That is, the controller 5, for example, as shown in FIG. 2B, preparesthe number of ON state pulse of the second pulse signal ST2corresponding to the operating status, and can indicate the variouskinds of operating status based on the prepared pulse number of thesecond pulse signal ST2 when the first pulse signal ST1 is ON state. Forexample, in the case where the normal operating status, abnormal status,muting status, override status and interlock status are indicated by thesecond pulse signal ST2, the number of the pulse is set to ‘1’, ‘2’,‘3’, ‘4’ and ‘5’ for each. Consequently, since the same output lineincluding the individual lines ST1, ST2 are suitable to provide three ormore kinds of operating status, that is, the number of output lines islower than the number of the indictable operating statuses, theincreasing of the number of output lines is reduced. Moreover, it ispreferred that the abnormal status is divided in more detail. The number(‘6’, ‘7’, . . . ‘N’) of the pulse of the second pulse signal ST2 may beprepared in accordance with the reason of the abnormal instead of theabnormal status ‘2’.

Further, it is preferred to be capable of selecting an output definitionfrom three states representing each inclusive status or ramified staterepresenting each ramified and concrete status.

For example, in ramification, in the case of the normal operatingstatus, a two-state output may be provided to discriminate between theoperation allowable status corresponding to all of the light axes beingpassed through and the operation non-allowable status corresponding towhere a part of or all of the light axes are blocked.

In the case of the special operating status, a three-state output may beprovided to discriminate between the muting status, the override statusand the interlock status.

In the case of the abnormal status, a two-state output may be providedto discriminate between the reset non-allowable status where the resetinput is not permitted and the reset allowable status where reset inputis permitted. Moreover, in the case of the reset non-allowable status, aplurality of status outputs may be provided to discriminate betweenoutput error, emitting error, receiving error, communicating error,muting error, interlock error and configuration error.

Further, it is preferred that the inclusive status output and theramified status output are mixed. For example, the normal operatingstatus output, the muting status output and the override status outputmay be provided.

It is preferred that the ramified status output such as the resetallowable status and the reset non-allowable status is provided insteadof providing the interlock status. Alternatively, in the case ofinterlock status, the reset allowable status output may be provided viaanother output terminal IR.

It is preferred that the operating status is provided by way of thecombination of ON/OFF signals, binary code (combination of the binarycode), via a plurality of output lines instead of the pulse signal.

Preferred embodiment of the processing machine with press machine 91.

A process system will be explained in the case where the multi-opticalaxis photoelectric sensor 1 is applied to the press machine 91 as anapplication example of the multi-optical axis photoelectric sensor 1shown in FIG. 2A. The safety control device 9 is connected to the pressmachine 91 and the like. The non-safety control device 4 is connected toan apparatus relating to process quality and process accuracy ofproducts such as a pressure sensor 44 etc. equipped in the press machine91, and is also connected to a mechanical lock 41 for fixing themovement of the press machine 91 mechanically. The non-safety controldevice 4 includes a timer (not shown in drawings) for measuring time onthe muting state.

Operation of Press System:

Referring to the flowchart in FIG. 3, the operation of the system willbe described.

Confirming Normal Initiation;

At a timing T1, an operator turns on the system. When the system isinitiated, a safety light curtain is formed between an emitting unit 2and a receiving unit 3 corresponding to the emitting unit 2. The lightcurtain includes a plurality of light beams from a plurality of emittingelements of the emitting unit 2 through a plurality of receivingelements of the receiving unit 3. An all-passing signal generated by thedistinguish means 33 is provided to a controller 5. On the other hand,detection means 34A to 34C performs a self-check to detect whether themulti-optical axis photoelectric sensor 1 is in an abnormal status ornot.

A operating status indicating means 53 of the controller 5 provides asignal representing the normal operation status to the non-safetycontrol device 4 in response to a confirmation that the multi-opticalaxis photoelectric sensor 1 is not in the abnormal status and theall-passing signal is received from the distinguish means 33, namelyconfirmation of the normal initiation.

After turning on, the operating status indicating means 53 does notindicate the operating status to the non-safety control device 4 untilthe operating status is confirmed and specified.

Normal Operating Status:

During the Normal Operating Status;

During normal operating, the control unit 50 of the controller 5 shownin FIG. 2, an output according to pass/block signal which is the resultof a determination by the distinguish means 33 (shown in FIG. 1) isprovided to an output.

In other words, when the all-passing signal is provided from thedistinguish means 33 (shown in FIG. 1) to the controller 5 on the normaloperating status, the control unit 50 provides the safety control signalrepresenting operation allowable (ON) to the safety control device 9.

On the other hand, during the normal operating status, when at least apart of the light beam is blocked by a part of a person body, thecontroller 5 provides the safety control signal representing operationnon-allowable (OFF) to the safety control device 9. At the time, thestatus of the controller 5 is shifted from the normal operating statusto an interlock status described below. The safety control device 9stops the press machine 91 immediately in response to receiving thesafety control signal representing an operation non-allowable. Arestarting of the press machine 91 will be described as follows.

Muting Input;

At timing T2, when an optical sensor detects an object (processedmaterial), a detection signal as a muting signal is provided (Mutinginput) from the optical sensor to the controller 5. In more detail, forexample, when the object is transported to the press machine 91 by wayof a belt conveyer and the like and the light curtain is disposed on andcrossed over the belt conveyer, a pair of optical sensors are disposedadjacent to the light curtain and at each of the upward end and thedownward end of the light curtain along the flow direction of the beltconveyer. When the optical sensor at the upward end detects a front endof the object, the optical sensor provides the muting signal to thecontroller 5.

Confirming the Muting Status;

After the timing T2, when the controller 5 receives the muting signaland receives the all-passing signal from the distinguish means 33, thestatus of the multi-optical axis photoelectric sensor 1 is shifted fromthe normal operating status to the muting status at timing T3. On theother hand, the operation status indicating means 53 provides a signalrepresenting the muting status to the non-safety control device 4 viathe output lines ST1, ST2. During the muting status, the control unit 50provides the safety control signal representing an operation allowableto the safety control device 9 regardless of the passing through/blocksignal from the distinguish means 33.

Deactivating Muting Status;

At timing T4, when the optical sensor at the downward end finishesdetecting the rear end of the object, the muting signal is not provided.The controller 5 recognizes the disconnection of providing the mutingsignal as the muting deactivating signal.

Confirming End of Muting->Normal Operating Status;

At timing T5, when the controller 5 recognizes that the multi-opticalaxis photoelectric sensor 1 is not in an abnormal status and receivesthe all-passing signal from the distinguish means 33, the muting statusis deactivated and is shifted to the normal operating status. On theother hand, operation status indicating means 53 provides a signalrepresenting the normal operating status to the non-safety controldevice 4 via the output lines ST1, ST2.

Confirming Muting Input and Muting Status;

At timing T6, when the optical sensor at the upward end detects anotherobject, the muting signal is provided to the controller 5. At timing T7,the status of the controller 5 is shifted to the muting status and thecontroller 5 confirms the status.

Confirming Initiation (in Case of Auto Reset);

When a momentary breaking of the power supply occurs, the muting statusis canceled and the control unit 50 provides the safety control signalrepresenting operation non-allowable to the safety control device 9.Consequently, the safety control device 9 stops the press machine 91. Attiming T8, a confirmation of normal initiation is automaticallyperformed. If the initiation is confirmed as normal, the multi-opticalaxis photoelectric sensor 1 operates the normal status (Auto reset).

At that time after the momentary breaking of the power supply on themuting status, when the object at the light curtain intercepts at leastone of any light beams of the multi-optical axis photoelectric sensor 1,the object remains at the light curtain since the conveyer stops in viewof the safety control signal representing operation non-allowable.Moreover, at least one of any light beams is intercepted, the status isnot shifted to the muting status although the muting signal is provided.Therefore, the object has to be removed from the light curtain. Attiming T9, an override signal is provided via an input terminal 9 shownin FIG. 2A, and the status of the controller 5 is shifted to an overridestatus. On the other hand, the operating status indicating means 53provides a signal representing the override status to the non-safetycontrol device 4 via the output lines ST1, ST2. On the override status,the controller 5 provides the safety control signal representingoperation allowable regardless of the passed through/blocked signal fromthe distinguish means 33. Thus, the object on the conveyer can beremoved from the light curtain. The requirement of shifting from thenormal operating status to the override status is that the muting signaland the override signal are provided, and the block signal is providedfrom the distinguish means 33.

When the object intercepting the light beam is removed and thecontroller 5 receives the all-passing signal from the distinguish means33, at timing T10, the status is shifted from the override status to thenormal operating status as shown in FIG. 3. On the other hand, theoperating status indicating means 53 provides a signal representing thenormal operating status to the non-safety control device 4 via theoutput lines ST1, ST2.

The detection means 34A to 34C periodically repeat to self-check as thementioned above from initiating of the system. At timing T11, when atleast one of any detection means 34A to 34C detects the abnormal status,the control unit 50 provides the safety control signal representing anoperation non-allowable to the safety control device 9 regardless of thepassed through/blocked signal. The safety control device 9 stops thepress machine 91 immediately in response to receiving the safety controlsignal representing operation non-allowable. On the other hand, theoperating status indicating means 53 provides the abnormal status to thenon-safety control device 4.

Reset Input;

When the operator solves a problem causing the abnormal status, attiming T12, the operator resets manually. After that, the multi-opticalaxis photoelectric sensor 1 operates on the normal operating status. Onthe other hand, the operating status indicating means 53 provides asignal representing shifting to the normal operating status to thenon-safety control device 4. At timing T13, the non-safety controldevice 4 can confirm the shifting from the abnormal status to the normaloperating status based on the signal from the operating statusindicating means 53.

It is preferred that the operating status indicating means 53 determineswhether the problem causing the abnormal status is solved or not, basedon the detection signals from the detection means 34A-34C. As theresult, if the problem is solved, a signal representing a resetacceptable status may be provided via the output lines ST1, ST2 oranother terminal 61.

Other Operation Example:

Other examples of the movement of the system will be described based ona timing chart shown in FIG. 4.

When the system is turned on and the system is initiated on the normaloperating status, a signal representing the normal operating status isprovided to the non-safety control device 4. At timing T21, thenon-safety control device can confirm a normal initiation of themulti-optical axis photoelectric sensor 1.

Interlock Status;

At timing T22, when at least a part of the light beams is blocked, thecontrol unit 50 provides the safety control signal representingoperation non-allowable to the safety control device 9. Then, the safetycontrol device 9 stops the press machine 91 immediately in response toreceiving the safety control signal from the control unit 50. The statusis an interlock status.

The interlock status may be categorized as follows. If at least one ofany light beams is blocked on the interlock status, the human body isunderstood to be at a hazardous source. In such a case, a reset inputfor releasing the interlock status should not be accepted. Therefore,one of the categorized interlock statuses is a non-releasable interlockstatus. On the other hand, in the case where all of the light beams arepassed through on the interlock status, a reset input for releasing theinterlock status is acceptable. Therefore, another of the ramifiedinterlock status is a releasable interlock status.

At timing T22, when at least a part of the light beams is blocked, theoperating status indicating means 53 provides a signal representing thenon-releasable interlock status to the non-safety control device 4 viathe output lines ST1, ST2.

At timing T23, the non-safety control device 4 confirms thenon-releasable interlock status of the multi-optical axis photoelectricsensor 1 based on the signal from the operating status indicating means53. If the multi-optical axis photoelectric sensor 1 receives a resetsignal for releasing the interlock status, the reset signal is ignoredon the non-releasable interlock status. Since the signal representingthe non-releasable interlock status is essentially the same as a signalrepresenting a status where at least one of any light beams is blocked,a common signal may represent both.

At timing T24, when the human body blocking the light beam moves and allof the light beams are passed through, the non-releasable interlockstatus is shifted to the releasable interlock status. At that time, theoperating status indicating means 53 provide a signal representing thereleasable interlock status to the non-safety control device 4 via theoutput lines ST1, ST2. As a result, at timing T25, the non-safetycontrol device can confirm the releasable interlock status based on thesignal from, the operating status indicating means 53. Of course, atthat time, the detection means 34A to 34C do not detect any problemscausing the abnormal status.

Manual Reset;

At timing T26 on the releasable interlock status, when an operatorperforms a predetermined reset operation, a reset input is provided tothe control unit 50 shown in FIG. 2 via an input terminal 62. When themulti-optical axis photoelectric sensor 1 receives the reset input, thestatus of the multi-photoelectric sensor is shifted to the normaloperating status. At that time, the operating status indicating means 53provides a signal representing the normal operating status to thenon-safety control device 4 via the output lines ST1, ST2. At timingT27, the non-safety control device 4 can confirm shifting to the normaloperating status based on the signal from the operating statusindicating means 53.

An example of applications utilizing the multi-optical axisphotoelectric sensor 1 is described as shown in FIGS. 5 to 7.

As the above-mentioned, an arm 102 shown in FIG. 5A rotates as shown inFIG. 5C. Then, the arm 102 transports an object W to a processingmachine M. An operational panel 106 is connected to the controller 5,the non-safety control device 4 and the safety control device 9.

As shown in FIGS. 5B and 5C, above a rod 105, a thru-beam optical sensor110 for detecting an upper end of the rod 105 is equipped. When arotating unit 103 is fixed by the rod 105 as shown in FIG. 5B, theoptical sensor 110 detects the top end of the rod 105. Thus, the statusof the multi-optical axis photoelectric sensor 1 is shifted to themuting status. On the other hand, when the rod 105 shown in FIG. 5D goesdown and the rotating unit 103 is not fixed, the optical sensor 110 doesnot detect the top end of the rod 105. Then, muting status is shifted.

A muting status in one of embodiments according to the present inventionis described as referring to a flowchart shown in FIG. 6.

In step S0, an operator O instructs suspending to the arm 102 by usingthe operational panel 106.

In step S1, the rotating unit 103 rotates to a predetermined suspendingposition toward the processing machine M. After the rotating unit 103 ispositioned at the predetermined suspending position, the rod 105 entersa hole of the rotating unit 103. The top of the rod 105 goes out fromthe opposite side of opening in the hole. Thus, the optical sensor 110detects the top of the rod 105. The controller 5 receives the signalfrom the optical sensor 110 as the muting input. In this case, if all ofthe light beams of the multi-optical axis photoelectric sensor 1 arepassed through, the status of the multi-optical axis photoelectricsensor 1 is shifted to the muting status. At the time, the operatingstatus indicating means 53 provides a signal representing the mutingstatus to the non-safety control device 4 via the output lines ST1, ST2.On the other hand, if the optical sensor 110 does not detect the rod105, the status is not shifted to the muting status.

In step S2, a determination of whether all of the light beams of themulti-optical axis photoelectric sensor 1 are passed through or not isexecuted. If the result of the determination is Yes, the step proceedsto the next step, step S3. On the other hand, if the result of thedetermination is No, the step goes back to the step S1. Therefore, ifthe operator O does not go out from the detection area A completely anda start button 107 is pushed, the rod 105 still remains and interceptsthe light beam of the optical sensor 105 since the pushing of the statebutton 107 is ignored. As that result, the arm 102 is fixed to provide asafe situation and preventing the stopping of the system needlessly areboth achieved.

After that, when the operator goes apart from the detection area A, allof the light beams are passed through in the detection area A. At thattime, an all-passing signal is provided from the controller 5 to thenon-safety control device 4 via an output line C/R. Then, the stepproceeds to the next step, step S3.

In step S3, when the operator O pushes the start button 107, the stepproceeds to the next step, step S4. In other words, as shown in FIG. 5D,the rod goes down in accordance with a signal representing the startfrom the start button 107. After that, since the optical sensor 110 doesnot detect the rod 105, the muting status is shifted to the normaloperating status.

Another embodiment according to the present invention will be describedas follows. In this embodiment, it is capable to indicate whether aninterlock is releasable or not, on an operational panel and the like.The method will be described as referring to the flowchart shown in FIG.7.

The operational panel includes a display means, for example, composed ofa Liquid Crystal Display (LCD).

In step S10, when at least one of any light beams of the multi-opticalaxis photoelectric sensor 1 is intercepted on the normal operatingstatus, the control unit 50 provides the safety control signalrepresenting operation non-allowable to the press machine as thehazardous source. The press machine is stopped in response to the safetycontrol signal. The status of the multi-optical axis photoelectricsensor 1 is shifted to interlock status.

In Step S11, a determination whether of the status is on the interlockstatus or not is made. If the determination is Yes, the step proceeds tostep S12.

In step S12, the distinguish means 33 detects the condition of passingor blocking light. The self-checking is performed by the detection means34A to 34C. In other words, when an operator is not present in thedetection area and the multi-optical axis photoelectric sensor 1 doesnot have a fault, the step proceeds to step S13.

In step S13, when other requirements for starting are met, for example,a detection pressure measured by a pressure sensor is within apredetermined range, the step proceeds to step S14.

In step S14, information representing that an interlock is releasable isindicated on the display means. The information allows an operator toknow the proper timing for pushing the button for releasing theinterlock.

It is preferred that the same signals can be provided via the terminals61, 62 for backup and verification.

In the above-mentioned embodiments, the controller 5 is installed in thereceiving unit 3. However, according to the present invention, theposition of the controller 5 is not limited. For example, as shown inFIG. 8, the controller 5B corresponding to the controller 5 may beseparate from the emitting unit 2 and the receiving unit 3. Or, thecontroller 5B is installed in the emitting unit 2.

The present invention is applicable for a multi-optical axisphotoelectric sensor which forms a light curtain for detecting a humanbody and the like penetrating into a predetermined area.

1. A multi-optical axis photoelectric sensor including a plurality oflight axes to provide a safety control signal corresponding to lightpass/block status of the plurality of light axes, comprising: adistinguish portion for distinguishing whether all of the plurality oflight axes are passed through or at least one of the plurality of lightaxes is blocked; a detector to detect an abnormal condition of the multioptical axis photoelectric sensor; a control unit to control the safetycontrol signal based on the result distinguished by the distinguishportion and the result detected by the detector, wherein the controlunit sets the safety control signal representing the resultdistinguished by the distinguish portion on a normal operating status,the control unit sets the safety control signal representing at leastone of the plurality of light axes is blocked regardless of the resultdistinguished by the distinguish portion on an abnormal status detectedby the detector, and the control unit sets the safety control signalrepresenting all of the plurality of light axes are passed throughregardless of the result distinguished by the distinguish portion on aspecial operating status; an operating status indicating portion forconfirming an operating status of the multi-optical axis photoelectricsensor from the normal operating status, the abnormal status and thespecial operating status and for providing a signal representing theconfirmed operating status of the multi-optical axis photoelectricsensor to an external device via the same output line regardless of thedetermined operating status; and wherein the operating status indicatingportion provides the signal to the external device via the same outputline in response to confirming of shifting of the operating status. 2.The multi-optical axis photoelectric sensor according to claim 1,wherein the same output line includes a plurality of individual lines,and the operating status indicating portion provides a first signalhaving a number of pulses corresponding to the operating status via oneof the plurality of individual lines and a second signal representingwhether the first signal is enabled or not via another of the pluralityof individual lines.
 3. The multi-optical axis photoelectric sensoraccording to claim 1, wherein the same output line includes a pluralityof individual lines, and the operating status indicating portionprovides binary code made by a combination of a plurality of ON/OFFstate signals via each of the plurality of individual lines.
 4. Themulti-optical axis photoelectric sensor according to claim 1, whereinthe control unit controls to shift the multi-optical axis photoelectricsensor to a muting status as the special operating status based onreceiving a muting input.
 5. The multi-optical axis photoelectric sensoraccording to claim 4, wherein the control unit controls to shift themulti-optical axis photoelectric sensor to an override status as thespecial operating status based on receiving a muting input and anoverride input.
 6. The multi-optical axis photoelectric sensor accordingto claim 4, wherein the control unit controls to shift the multi-opticalaxis photoelectric sensor to an override status as the special operatingstatus based on receiving a muting input and an override input where thedistinguish portion distinguishes that at least one of the plurality oflight axes is blocked.
 7. The multi-optical axis photoelectric sensoraccording to claim 1, wherein the control unit controls to shift themulti-optical axis photoelectric sensor to a muting status as thespecial operating status based on receiving a muting input where thedistinguish portion distinguishes that all of the plurality of lightaxes are passed through.
 8. The multi-optical axis photoelectric sensoraccording to claim 1, wherein the operating status indicating portiondoes not indicate the operating status of the multi-optical axisphotoelectric sensor or indicates unidentified operating status untilverification of shifting the operating status at a power on period. 9.The multi-optical axis photoelectric sensor according to claim 1,wherein the operating status indicating portion does not indicate theoperating status of the multi-optical axis photoelectric sensor orindicates unidentified operating status until verification of shiftingthe operating status at shifting period.
 10. A multi-optical axisphotoelectric sensor including a plurality of light axes to provide asafety control signal corresponding to light pass/block status of theplurality of light axes, comprising: a distinguish means fordistinguishing whether all of the plurality of light axes are passedthrough or at least one of the plurality of light axes is blocked; adetection means for detecting an abnormal condition of the multi-opticalaxis photoelectric sensor; a control means for controlling the safetycontrol signal based on the result distinguished by the distinguishmeans and the result detected by the detection means, wherein thecontrol means sets the safety control signal representing the resultdistinguished by the distinguish means on a normal operating status, thecontrol means sets the safety control signal representing at least oneof the plurality of light axes is blocked regardless of the resultdistinguished by the distinguish means on an abnormal status detected bythe detection means, and the control means sets the safety controlsignal representing all of the plurality of light axes are passedthrough regardless of the result distinguished by the distinguish meanson a special operating status; an operating status indicating portionfor confirming an operating status of the multi-optical axisphotoelectric sensor from the normal operating status, the abnormalstatus and the special operating status and for providing a signalrepresenting the confirmed operating status of the multi-optical axisphotoelectric sensor to an external device via the same output lineregardless of the determined operating status; and wherein the operatingstatus indicating portion provides the signal to the external device viathe same output line in response to confirming of shifting of theoperating status.